Docosahexaenoic acid and its derivatives are known, in their mixed form, as a remedy for complications of diabetes (Japanese Patent Application Laid Open (Kokai) No. 60-24610) or hemorrhoid (Japanese Patent Application Laid Open (Kokai) No. 61-24518), a stimulant of lipoxygenase metabolism (Japanese Patent Application Laid Open (Kokai) No. 63-230632), an ameliorant for brain functions (Japanese Patent Application Laid Open (Kokai) No. 1-27982), an anticancer agent (Japanese Patent Application Laid Open (Kokai) No. 1-153629), a remedy for capsular nephritis (Japanese Patent Application Laid Open (Kokai) No. 2-235811), and an antiarrhythmic agent (Japanese Patent Application Laid Open (Kokai) No. 4-29928).
Polyene phosphatidyl choline preparation is generally accepted as a remedy for hepatitis. Mevalotin or mevinolin type compounds have been used for inhibiting biosynthesis of cholesterol. Linoleic acid and linolenic acid have been widely used for removing cholesterol in blood serum and for preventing arteriosclerosis.
Among a few drugs for hepatic diseases, polyene phosphatidyl choline preparation has been used for a long time but possesses only mild cholesterol reducing efficacy, though it is almost satisfactory in its safety. The preparations of mevalotin or mevinolin type compounds have been highly evaluated owing to their strong inhibition of the production of cholesterol at the intermediate stage. However, since they inhibit the production of intermediary sterol compounds, they tend to reduce also the production of neurotransmitters and hormones which are essential for human body. Therefore, the use of this type of preparations are limited.
Poly unsaturated fatty acids are substances which would bring a preventive effect against arteriosclerosis only after a long period dosage. Also, their mild effects are overestimated without precise experiments as a pharmaceutical drug using pure single substance. With a decease of fish intake in Japan, the patients of hypohepatia, i.e., various hepatic diseases such as hepatocirrhosis, hepatocellular carcinoma, hepatitis and adipohepatia have increased so that it is desired to provide drugs for improving hepatic functions including a drug for removing cholesterol.
Hepatitis is caused by some viruses and various toxic substances, and brings hepatocytolysis. Especially, fulminant hepatitis brings severe subjective symptoms such as nausea, vomit, and cenesthopathia. It also brings clinical symptoms such as hyperthermia, hyperleukocytosis, crucially positive C-reactive protein and serious icterus, and sometimes causes death at the early stage. Even if the patient does not die, chronic hepatitis often moves to hepatocirrhosis and hepatocarcinoma, and brings many social problems.
For treating viral hepatitis such as A-type, B-type, C-type, O-type and E-type ones, it is proposed to dose interferons. However, the effects and appropriate dosage of interferons are not yet confirmed. Its combination with a steroid has also been tried but is reported to cause some adverse effects. Accordingly, the patients of hepatitis are at present treated mainly with a supplementary therapy, i.e., liver-protective therapy without any effective drug for hepatitis or any drug for inhibiting induction of hepatitis which accompanies no adverse effect (MEDICAL DIGEST, Vol. 39 (4) , 1990) .
Therefore, the object of the present invention is to provide an effective drug for improving hepatic functions and for treating and preventing hepatitis including fulminant hepatitis, hepatocirrhosis, hepatocellular carcinoma, and hepatic insufficiency with little toxicity.